Lab-on-a-chip and micro-total-analysis systems have experienced a significant increase in interest in the biomedical and chemistry areas during the last decade. Effort has been made to develop new technologies enabling labs to be shrunk and integrated onto single chips. This emerging technology has proven to be very promising, and is often referred as “microfluidics”. Microfluidics allows fluid flow control and mixing of fluids on chips using microchannels, into which fluids are injected. Such chips integrate many functions on a single substrate which not only allows an entire experiment to be built on a small chip, but also allows a large amount of parallel experiments to be performed simultaneously using very small volumes of fluids in a limited amount of time.
Microfluidic circuits require microvalves, i.e. tiny valves that are one of the key building blocks for making complex microfluidic integrated circuits. Microvalves are used to direct and pump fluids. Typically, the microvalve is used to block, open, or regulate the passage of the fluid in the microchannel.
For example, certain known microvalves comprise a membrane which is displaced into a channel by electrostatic force in order to control the flow of a fluid propagating in the channel. A solid film of electrically conductive material electrode is typically deposited on the membrane in order to form a first of two solid electrodes. However, because of the stretching of the membrane, the electrode layer is subject to delamination and fatigue problems, in addition to limiting the stretching of the membrane.
Additionally, for such microvalves to successfully operate, the channels within which they are formed must be accurately formed. Challenges often exist with the microfabrication of the substrates within which the microcircuits are formed. For example, when using usual wet-etching techniques to form channels in a substrate, the sidewalls of the etched structures in amorphous material tend to be rounded. It can however be desired to form a straight or angled sidewall, which is difficult with known etching techniques.
Therefore, there remains a need for improved microfluidic devices.